Apparatus for automatically filling well casing



Sept. 13, 1955 R, C, BAKER 2,717,647

APPARATUS FOR AUTOMATICALLY FILLING WELL CASING 2 Sheets-Sheet l Filed June 25, 1952 /W/ly. i.'

R. C. BAKER sept. 13, 1955 APPARATUS FOR AUTOMATICALLY FILLING WELL CASING 2 Sheets-Sheet 2 Filed June 23, 1952 United States Patent O APPARATUS FR AUTMATICALLY FILLING WELL CASING Reuben C. Baker, Coalinga, Calif., assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application .lune 23, 1952, Serial No. 295,007

Claims. (Cl. 166225) The present invention relates to subsurface well apparatus, and more particularly to apparatus for filling a string of well casing, or the like, with fluid in the well bore as it is lowered therewithin.

An object of the present invention is to provide an improved apparatus for automatically filling well casing, f

as it is lowered through the fluid in the well bore to predetermined levels that are less than the levels of the iluid in the well bore externally of the casing.

Another object of the invention is to provide a differential valve in subsurface well apparatus for automatically iilling well casing with well bore fluid, in which the valve can still be shifted to an ineffective position in the event junk, debris and the like in the well bore jams the valve mechanism. A further object of the invention is to provide a subsurface valve device for automatically filling well casing with well bore fluid, which has a comparatively large passage area, thereby allowing relatively large particles, debris and the like to pass through the device without plugging it. Such large passage area also minimizes erosive wear on the parts occasioned by fiuid flowing through the device. In this connection, the device allows the fluid to flow through it with little turbulence,

Yet another object of `the invention is to provide a comparatively simple, sturdy and economical subsurface valve device for filling well casing with the well bore fluid as the casing is being lowered therewithin.

Still a further object of the invention is to provide a back pressure valve in a casing string, and to prevent such valve from closing until desired by means of a comparatively simple valve mechanism that can automatically allow the casing string to fill with well bore fluid to a predetermined level lower than the external uid level, or to automatically allow the casing string to fill completely with ythe well bore fluid. i

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but ,it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined 4by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section through an apparatus embodying the invention, disclosed as secured to the lower end of a casing section and disposed in a Well bore, the parts of the device being in open position to allow ow of fluid therethrough;

Fig. 2 is a view similar to Fig. 1, with the valve device in closed position;

Fig. 3 is a View similar to to Figs. '1 and 2, illustrating the valve device shifted to an ineffective position and a back pressure valve freed for engagement with a companion seat; f

2,7l74? Patented Sept. 13, 1955 "ice Fig. 4 is an enlarged longitudinal section illustrating the device in the same operative position as in Fig. l;

Fig. 5 is a cross-section taken along the line 5 -5 on Fig. 4.

The apparatus A disclosed in the drawings is designed to form part of a string of well casing B, or similar well conduit to be run in a well bore C. As specifically illustrated, it is embodied in a casing shoe forming the lower terminus of the casing string. However, i't is to be understood that this apparatus could also be incorporated in lthe casing string B at an intermediate point along its length, in which event it would be considered to be a casing collar.

The apparatus includes an outer tubular member 10 having an upper threaded box 11 for threaded attachment to the lower end of an adjacent casing section B. The tubular member has a cementititious plug 12 cast therein, ribs 1 3 on the plug being formed during the casting operation by internal grooves 14 in the tubular member, in order to inseparably unite the parts against relative movement. The lower end of the cementitious plug 12 is rounded, to provide a guiding nose 15 for facilitating passage of the casing string through obstructions and restrictions in the well bore C as it is being lowered therewithin.

The cementitious plug 12 has a central passage 16 therethrough. This passage is surrounded by a valve seat 17 cast within'the plug and adapted to be engaged by a back pressure valve element 18, in the form of a ball, preferably buoyant in the cement slurry. In order to prevent leakage between the ball and the seat, a seal ring 19 may be clamped to the seat 17 by a retainer ring 20, which is held in appropriate position by a tubular stop member 21 secured within the cementitious plug 12. This stop member has inwardly directed and circumferentially spaced lugs or fingers 22 upon Which the ball valve member 18 may engage when shifted in a downward direction out of contact from its companion seat 17.

It is desired to maintain the ball valve member 18 out of engagement with its seat 17 during lowering of the casing string B through the fluid in the well bore C, for Vthe purpose of allowing the well bore fluid to ow upwardly through the apparatus and into the casing string. It is also desired to controllably fill the casing string B with the well bore fluid, but to a level that is preferably less than the level of the Huid externally of the casing string. To accomplish these objectives, a valve device is embodied in the tubular member 10 below its back pressure valve portion 18. This device includes a tubular housing 23 having external grooves 24 receiving ribs 25 in the cementitious plug to prevent relative movement between the two. The housing, as illustrated, is formed of an upper section 23a piloted into a lower section 2 3b. The upper section has a shoulder 26 engaging the lower end of the stop member 21 to properly locate ,the parts with respect to each other.

The lower housing portion 23b has a spider 27 integral with it, or otherwise united to it, this spider being provided with one or more ports or openings 28 therethrough to Iallow well fluid to iiow upwardly into the housing 2 3. As stated above, it is preferred to have the back pressure ball initially prevented from engaging its seat. This objective is accomplished by threading the upper end of a tie rod 29 into the ball 18, the lower end of the tie rod being piloted within va valve seat 30, to which it is releasably secured by a frangible connecting element 31, in the form of a shear screw threaded through the valve seat 3Q and into the rod 29. The valve seat 30 has a depending or stern portion 32 extending through the hub 33 of the spider, this stern portion being Yreleasably secured to the spider vby one or more -frangible elements 34, in the form of shear screws threaded transversely through the hub 33 and into the stem portion 32. The back pressure valve element 1S, tie rod 29 and valve seat 3i) are thereby secured to the spider 27 and the valve housing 23, which precludes upward movement of the ball valve element 18 into engagement with its seat 17. In addition to such upward movement being prevented by the shear screws 34 securing the stem 32 to the spider 27, the parts are incapable of moving upwardly by virtue of a split snap ring 35 disposed in a peripheral groove 36 in the stem 32 and engaging the lower end of the spider hub 33.

lt is to be noted that uid can flow upwardly through the spider ports or openings 28, through the valve housing 23, around the valve seat 3i) and tie rod 29, continuing on up through the arcuate spaces between the stop lugs 22 and around the ball valve member i8, and on up through the back pressure valve seat 17 into the casing sections B thereabove. The ability of the uid to ow upwardly in this manner is dependent upon the location of a tubular valve member 37 that is slidable within the upper valve housing portion 23a between an upper position in engagement with the lower end 38 of the stop member 21, in which the lower end of the valve member 37 is disposed substantially above the valve seat 3i) (Figs. l and 4), and a lower position in which the lower inner sealing edge 39 of the valve member is in engagement with the tapered valve seat surface 40 (Fig. 2).

The upper housing portion 23a has an upper enlarged cylindrical wall 4l and a lower cylindrical wall 42 of smaller diameter than the upper wall. Between these two walls is provided a transverse shoulder 43. The valve member 37 has a corresponding large diameter upper portion 44 adapted to slide along the upper wall 41, and a smaller diameter portion 45 slidable along the lower cylindrical wall 42. When the valve member 37 moves in a downward direction, to place its sealing edge 39 in engagement with the valve seat surface 40, for the purpose of preventing passage of iluid through the apparatus, a transverse shoulder 46 on the larger diameter portion 44 is disposed in spaced relation to and above the housing shoulder 43 (Fig. 2), for a purpose that will be described hereinafter.

Suitable slidable type of seals are provided between the cylindrical walls 4l, 42 of the upper housing portion 23a and the valve member 37. Thus, rubber or rubberlike seal rings 47, that may be of round cross-section, are disposed in one or more peripheral grooves 48 in the large diameter' upper valve member portion 44 for slidable sealing along the larger diameter cylinder wall 41. Similar seal ring or rings 49 are provided in ring grooves 5t? in the lower valve member portion 45 for slidable sealing against the wall 42 of the smaller diameter cylindrical portion of the valve housing 23. These seals 47, 49 cooperate with the valve member 37 and housing 23 to form a confined annular cylindrical space 51 into which the well fluid cannot enter.

The tubular valve member 37 has an inside diameter which is substantially greater than the diameter of the tie rod 2?, to provide a comparatively large passage area 52 through which fluid can flow. Thus, when the valve member 37 is in its upward position out of engagement from the companion seat 30, uid can pass upwardly through the spider ports or openings 28, around the valve seat 36 and through the annular space S2 between the tie rod 29 and valve member 37, continuing on upwardly around the back pressure ball valve element 18 and through the back pressure valve seat 17 into the casing sections B thereabove. It is to be noted that in pursuing this path, the iluid can flow smoothly and does not have to partake of any abrupt changes in direction that would create turbulence and tend to cause erosive wear on the parts.

In View of the fact that the smaller cylinder 42 has a lesser diameter than the larger cylinder 41, and the lower portion 45 of the valve member 37 has a correspondingly lesser diameter than the diameter of the upper portion 44 of the valve member, the downwardly facing area of the valve member over which fluid can act, to urge the valve member 37 in an upward direction, is `substantially less than the upwardly facing area over which the fluid above the valve member can act. Thus, the annular area R between the inner wall 53 of the valve member and the smaller diameter cylinder wall 42 is less than the annular area S between the inner wall 53 of the valve member and the larger diameter wall 41. Accordingly, the fluid under pressure below the valve member, which corresponds to the hydrostatic head of fluid externally of the casing string B, is acting over the area R, to urge the valve member 37 in an upward direction out of engagement from its companion seat 30. The pressure of the fluid within the casing string B, which corresponds to the hydrostatic head of fluid therewithin, is acting in a downward direction over the area S of the valve member 37, tending to urge the latter in a downward direction into engagement with the valve seat 30. A balanced condition on the valve will be realized when the pressure acting upwardly on the valve member over the area R is equal to the pressure acting on the valve member in the opposite direction over the area S. Since the area R is less than the area S, a balanced condition will be obtained when there is a lesser pressure internally of the casing string B than exists externally thereof. Expressed by way of formula, a balanced condition will exist when:

P1R=P2S in which P1=the hydrostatic head of fluid externally of the well casing; and

Pz=the hydrostatic head of fluid internally of the well casing. The hydrostatic heads of iluid externally and internally of the well casing will, therefore, be inversely proportional to the areasS and R. Since the area S is greater than the area R, the hydrostatic head of i'luid internally of the well casing B will be less than the hydrostatic head of fluid externally of the well casing. As the hydrostatic head of well liuid within the well casing increases to a sufficient extent it will shift the valve member 37 downwardly into engagement with the valve seat 30, preventing further upward passage of iluid into the well casing, until the casing string has been lowered in the Well fluid to a further extent.

The apparatus is run in the well bore with the parts occupying the relative positions disclosed in Figs. l and 4. During such lowering, the hydrostatic head of fluid externally of the well casing will act over the area R of the valve member 37 to shift it out of engagement from the Valve seat 30, or to open position, allowing the fluid to ow upwardly into the casing string B. If the casing string is brought to rest, the uid will flow therewithin until it rises to a level satisfying the aforenoted equation, and when the level tends to exceed the amount indicated by the equation, then the pressure of the lluid within the well casing will shift the valve member 37 downwardly into engagement with the valve seat 39, as disclosed in Fig. 2, thereby preventing further passage of fluid upwardly into the well casing. lf the descent of the casing string in the well bore fluid is recommenced, the valve 37 will again slide upwardly to open position, as indicated in Figs. l and 4, and additional fluid will enter the casing string. The above actions will continue, with the valve 37 shifting between open and closed positions until the casing has been lowered to the desired depth in the well bore. The level of the fluid in the well casing B, however, will always be maintained at a lower point than the level of the fluid in the well bore externalh of the well casing, depending on the relationships of the aforenoted areas R and S. During all or" this time, the tie rod 29, valve seat 3) and spider mechanism 27 is preventing the back pressure valve member 18 from engaging its companion seat 17, avoiding interference with the upward flow of uid in the casing string. i

After the casing has reached its desired depth in the well bore, the control valve mechanism 37 30 for determining the height to which the liquid level will be allowed to rise in the casing string is no longer needed, but the back pressure valve element 1S should be released, so that it can thereafter perform its attendant function. Accordingly, the casing string can now be illed completely with uid, which will urge and maintain the valve member 37 in a downward direction in sealing engagement with the valve seat 30, and pressure then applied to the fluid in the well casing. Such pressure acts downwardly over the area S of the valve member 37 and also over the upper surface of the valve seat 30, urging them in a downward direction, this downward force being transmitted through the valve seat to the shear screws 31, 34. When the yforce is suicient to overcome the shear strength of these screws, they are disrupted, disruption of the upper shear screw 31 freeing the tie rod 29 and allowing the ball valve member 1S to shift upwardly into engagement with its seat 17. The disruption of the lower shear screws 34 attaching the valve seat stem 32 to the spider 27 allows the valve member J7 and the valve Seat 30 to shift downwardly along the valve hous- 'ing 23 as a unit, until the shoulder 46 on the valve member engages the housing shoulder 43. When this occurs, the valve seat 3() is then pumped downwardly to a greater extent, until a shoulder on the upper portion of the valve seat member 3i) engages the upper end of the spider hub 33, the valve seat 30 then occupying a position spaced downwardly away from the sealing edge 39 of the valve member 37 (see Fig. 3). The valve member 37 is, accordingly, now in an open position, iiuid pumped downwardly through the casing string B being capable of passing through the valve member 37 and around the valve seat 34B for discharge through the spider ports or openings 28 and from the casing shoe A. In the event that the fluid now tends to iiow in a reverse direction back into the casing string, such action is precluded by the upward movement of the back pressure valve member 18 into engagement with its companion seat 17.

As stated above, the relationship between the areas R, S of the downward and upwardly facing pressure actuatable surfaces of the valve member 37 determines the level to which the liuid in the well casing B can rise with respect to the fluid level externally of the casing string. If these areas are made equal, then the well casing string will be able to lill with the well bore uid to a level equalling that of the uid externally of the well casing. need not be used at all. For that matter, if the seal rings are omitted, then a confined space 51 would no longer be present into which the well uid cannot enter. Instead, the well bore fluid can also enter such space by flowing between the housing 23 and the valve member 37, the pressure below the valve member 37 then being capable of acting over an area equal to lthe area over which the pressure above the valve member can act. Under these circumstances, the apparatus is useful to maintain the back pressure valve member 18 from its seat 17 during lowering of the casing string within the well bore, whereupon the application of sufficient presf -sure in a downward direction on the internal casing fiuid will shear the screws 31, 34 to free the back pressure valve element 18 for subsequent engagement with the valve seat 17.

The differential valve mechanism 37 is also useful in the absence of the back pressure valve 18, in order to control the filling of the well casing string B .to levels less than the external fluid level. After `.the casing has been lowered to the required depth in lthe well bore, the application of sufticient pressure to the iiuid within the casing string will shear the screws 34 holding the valve seat 3 0 to the spider 27 and allow the valve seat to shift downwardly out vof engagement from the valve ln this event, of course, the seal rings 47, 49 v member 37, in the manner .described above (Fig. 4), which then allows the downward pumping or tlowing of the well iluid within the well casing from the casing shoe A. Even if the areas R and S are made equal to each other, and the back pressure valve member 18 omitted, the device is still operable to allow the well casing to lill with uid, but to preclude downward passage of fluid from the well casing until desired, this latter action being able to occur only after the valve seat 30 has been freed from the spider 27 and shifted downwardly, in the manner described above.

It is, accordingly, apparent that an yapparatus has been provided for automatically filling Well casing with fluid, and such filling can be predetermined and preselected, so that the fluid level internally of the casing string is substantially less than that externally of the casing string. The arrangement of parts is comparatively simple, allowing them to be made in an economical manner and relatively strong, capable of withstanding safely all loads or forces normally encountered in deep wells, Large passage areas are provided through the apparatus, which will minimize erosion and prevent inadvertent plugging of the apparatus. If any elements in the well bore happen to become jammed between the valve member 37 and its companion seat 30, the apparatus can still be released, since suflicient pressure can be imp arted to the iiuid within the Well casing to still' shift the valve member 37 in a downward direction, for the purpose of shearing the screws 31, 34. The jamming elements will serve, in eect, to couple the valve member 37 to the valve seat 30, the passage remaining between the valve member and valve seat throttling the ow, enabling fluid pumped at an ample rate to build up enough back pressure above the valve member 37 to overcome the -shear strength of the screws 31, 34 and thereby release the back pressure valve member 18.

T he inventor claims:

1. In well apparatus: a conduit string to be disposed in a well bore, said conduit string including a tubular member; a valve seat positioned interiorly of said tubular member; a tubular valve member having a passage extending therethrough and slidable along the inner wall of said tubular member into engagement with said seat to prevent flow of fluid through said passage and out of engagement with said seat to permit flow of uid through said passage; said valve member having a first uid pressure actuatable surface subject to the pressure of uid above said valve member to urge said valve member downwardly into engagement `with said seat; said valve member having a second tiuid pressure actuatable surface `subject to the pressure of fluid below said valve member to urge said valve member upwardly out of engagement from said seat; said first surface having a substantially greater area than said `second surface.

2, In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a valve-seat positioned interiorly of said tubular member; a tubular valve member slidable along the inner wall of said tubular member into and out of engagement with said seat, said valve member having a passage extending therethrough; said valve member having a rst uid pressure actuatable surface subject to the pressure of liuid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having a second iluid pressure actuatable surface subject to the pressure of fluid below said valve member to urge `said valve member upwardly out ,of engagement from said seat; said rst surface having a substantially greater area than said second surface; and means releasably securing said valve seat to said tubular member, in order that iluid pressure above ksaid valve member acting on said valve member, after .engagement of said -valve member with said seat, will release said securing means, thereby enabling said valve member and seat to shift downwardly relative to said tubular member.

3. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a valve seat positioned interiorly of said tubular member; a tubular valve member slidable along the inner wall of said tubular member into and out of engagement with said seat, said valve member having a central passage extending completely therethrough; and means releasably securing said valve seat to said tubular member, in order that uid pressure above said valve member acting on said valve member, after engagement of said valve member with said seat, will release said securing means, thereby enabling said valve member and seat to shift downwardly relative to said tubular member.

4. In well apparatus: a conduit string to be disposed in a well bore, said conduit string including a tubular member; a housing in said member and having an inner cylindrical wall; a valve seat positioned interiorly of said tubular member; a tubular valve member having a central passage extending therethrough and slidable along said cylindrical wall into engagement with said seat to prevent ow of iluid through said passage and out of engagement with said seat to permit flow of fluid through said passage; said valve member having an annular upwardly facing surface subject to the pressure of fluid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having an annular downwardly facing surface subject to the pressure of iluid below said valve member to urge said valve member upwardly from engagement with said seat; said upwardly facing surface having a substantially greater area than said downwardly facing surface.

5. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a housing in said member and having an inner cylindrical wall; a valve seat positioned interiorly of said tubular member; a tubular valve member slidable along said cylindrical wall into and out of engagement with said seat, said valve member having a central passage extending therethrough; said valve member having an annular upwardly facing surface subject to the pressure of uid above said Valve member to urge said valve member downwardly into engagement with said seat; said valve member having an annular downwardly facing surface subject to the pressure of fluid below said valve member to urge said valve member upwardly from engagement with said seat; said upwardly facing surface having a substantially greater area than said downwardly facing surface; and means releasably securing said valve seat to said housing in order that uid pressure above said valve member acting on said valve member, after engagement of said valve member with said seat, will release said securing means, thereby enabling said valve member and seat to shift downwardly relative to said tubular member.

6. In well apparatus: a conduit string to be disposed in a well bore, said conduit string including a tubular member; a housing in said member and having an upper inner cylindrical wall and a lower inner cylindrical wall of lesser diameter than said upper wall; a valve seat posi tioned interiorly of said tubular member; a tubular valve member slidable along said walls and having upper and lower portions of external diameters conforming to said upper and lower walls, respectively; said valve member having a passage extending therethrough; said valve member being movable downwardly along said housing into engagement with said seat to close said passage and up wardly out of engagement from said seat to open said passage.

7. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a housing in said member and having an upper inner cylindrical wall and a lower inner cylindrical wall of lesser diameter than said upper wall; a valve seat positioned interiorly of said tubular member; a tubular valve member slidable along said walls and having upper and lower portions 0f external diameters conforming to said upper and lower walls, respectively; said valve member having a passage extending therethrough; said valve member being movable downwardly along said housing into engagement with said seat to close said passage and upwardly out of engagement from said seat to open said passage; and seal means between said valve member and walls providing a coniined space therebetween into which uid cannot enter while the apparatus is in a well bore; said housing being imperforate between said seal means.

8. In well apparatus: a tubular member having means E thereon for securing said member in a conduit string; a

housing in said member and having an upper inner cylindrical wall and a lower inner cylindrical wall of lesser diameter than said upper wall; a valve seat positioned interiorly of said tubular member; a tubular valve member slidable along said walls and having upper and lower portions of external diameters conforming to said upper and lower walls, respectively; said valve member having a passage extending therethrough; said valve member being movable downwardly along said housing into engagement with said seat and upwardly out of engagement from said seat; and means releasably securing said valve seat to said tubular member, in order that fluid pressure above said valve member acting on said valve member, after engagement of said valve member with said seat will release said securing means, thereby enabling said valve member and seat to shift downwardly relative to said tubular member.

9. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a valve seat in said tubular member; a tubular valve member slidable along said tubular member and into and out of engagement with said seat, said valve member having a passage extending therethrough; said valve member having a first fluid pressure actuatable surface subject to the pressure of iluid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having a second fluid pressure actuatable surface subject to the pressure of uid below said valve member to urge said Valve member upwardly out of engagement from said seat; said tirst surface having a substantially greater area than said second surface; means releasably securing said valve seat to said tubular member, in order that engagement of said valve member with said seat enables iluid pressure above said valve member to act on said valve member and release said securing means; and means engageable with said valve member to limit its downward movement, after release of said securing means, to a lesser distance than that of the downward movement of said valve seat, to enable said valve seat to move downwardly out of engagement from said valve member.

10. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a housing in said member and having an inner cylindrical wall; a valve seat in said tubular member; a tubular valve member slidable along said cylindrical wall into and out of engagement with said seat, said valve member having a central passage extending therethrough; said valve member having an annular upwardly facing surface subject to the pressure of Huid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having an annular downwardly facing surface subject to the pressure of fluid below said valve member to urge said valve member upwardly from engagement with said scat; said upwardly facing surface having a substantially greater area than said downwardly facing surface; a perforate member extending transversely from said housing and in which said valve seat is slidable; means releasably securing said valve seat to said perforate member, in order that engagement of said valve member with said seat enables fluid pressure above said valve member to release said securing means; and means engageable with said valv.; member to limit its downward movement, after release of said securing means, to a lesser distance than that of the downward movement of said valve seat, to enable said valve seat to move downwardly out of engagement from said valve member.

11. ln well apparatus: a tubular member having means thereon for securing said member in a conduit string; a valve seat in said tubular member; a tubular valve member slidable along said tubular member into and out of engagement with said seat, said valve member having a passage extending therethrough; said valve member having a rst fluid pressure actuatable surface subject to the pressure of iluid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having a second fluid pressure actuatable surface subject to the pressure of lluid below said valve member to urge said valve member upwardly out of engagement from said seat; said first surface having a substantially greater area than said second surface; and means releasably securing said valve seat to said tubular member, in order that engagement of said valve member with said seat enables fluid pressure above said valve member to act on said valve member and release said securing means, enabling said valve member and seat to shift downwardly in said tubular member; back pressure valve means in said tubular member capable of closingto prevent ilow of fluid in one direction through said tubular member; and means releasably interconnecting said baci; pressure valve means and valve seat to maintain said back pressure valve means in open position.

l2. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a valve seat in said tubular member; a tubular valve member slidable along said tubular member into and out of engagement with said seat, said valve member having a passage extending therethrough; means releasably securing said valve seat to said tubular member, in order that engagement of said valve member with said seat enables fluid pressure above said valve member to act on said valve member and release said securing means, enabling said valve member and seat to shift downwardly in said tubular member; back pressure valve means in said tubular member capable of closing to prevent flow of uid in one direction through said tubular member; and means releasably interconnecting said back pressure valve means and valve seat to maintain said back pressure valve means in open position.

13. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a housing in said member and having an upper inner cylindrical wall and a lower inner cylindrical wall of lesser diameter than said upper wall; a valve seat in said tubular member; a tubular valve member slidable along said walls and having upper and lower portions of diameters conforming to said upper and lower walls, respectively; said valve member having a passage extending therethrough; said valve member being movable downwardly along said housing into engagement with said seat and upwardly out of engagement from said seat; back pressure valve means in said tubular member capable of closing to prevent ow of fluid in one direction through said tubular member; and means releasably interconnecting said back pressure valve means and valve seat to maintain said back pressure valve 6 means in open position.

14. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a valve seat in said tubular member; a tubular valve member slidable along said tubular member into and out of engagement with said seat, said valve member having a passage extending therethrough; said valve member having a rst fluid pressure actuatable surface subject to the pressure of iluid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having a second uid pressure actuatable surface subject to the pressure of uid below said valve member to urge said valve member upwardly out of engagement from said seat; said first surface having a substantially greater area than said second surface; means releasably securing said valve seat to said tubular member, in order that engagement of said valve member with said seat enables fluid pressure above said valve member to act on said valve member and release said securing means; means engageable with said valve member to limit its downward movement, after release of said securing means, to a lesser distance than that of the downward movement of said valve seat, to enable said valve seat to move downwardly out of engagement from said valve member; back pressure valve means in said tubular member capable of closing to prevent flow of fluid in one direction through said tubular member; and means releasably interconnecting said back pressure valve means and valve seat to maintain said back pressure valve means in open position.

15. In well apparatus: a tubular member having means thereon for securing said member in a conduit string; a housing in said member and having an inner cylindrical wall; a valve seat in said tubular member; a tubular valve member slidable along said cylindrical wall into and out of engagement with said seat, said valve member having a central passage extending therethrough; said valve member having an annular upwardly facing surface subject to the pressure of fluid above said valve member to urge said valve member downwardly into engagement with said seat; said valve member having an annular downwardly facing surface subject to the pressure of uid below said valve member to urge said valve member upwardly from engagement with said seat; said upwardly facing surface having a substantially greater area than said downwardly facing surface; a perforate member extending transversely from said housing and in which said valve seat is slidable; means releasably securing said valve seat to said perforate member, in order that engagement of said valve member with said seat enables fluid pressure above said valve member to release said securing means; means engageable with said valve member to limit its downward movement, after release of said securing means, to a lesser distance than that of the downward movement of said valve seat, to enable said valve seat to move downwardly out of engagement from said valve member; back pressure valve means in said tubular member capable of closing to prevent ow of Huid in one direction through said tubular member; and means releasably interconnecting said back pressure valve means and valve seat to maintain said back pressure valve means in open position.

References Cited in the le of this patent UNITED STATES PATENTS 334,326 Acheson Ian. 12, 1886 457,056 McNeil et al Aug. 4, 1891 2,300,854 Allen et al. Nov. 3, 1942 2,593,520 Baker et al. Apr. 22, 1952 

